Irish writer-director John Carney believes in the healing powers of song. Boy, does he ever. “Once,” his 2006 indie smash, was all about that, and so is his new film “Begin Again,” which was originally titled “Can A Song Save Your Life?”

His answer, of course, is yes. For those of us who prefer our music lessons with a bit less treacle, the verdict is still in. “Begin Again” feels more like a glorified retread of “Once” than something freshly imagined.

Mark Ruffalo, in a rare not-wonderful performance, plays Dan Mulligan, a dissolute music industry producer in New York, separated from his wife (Catherine Keener) and estranged from his daughter (Hailee Steinfeld), who finds career and personal redemption in promoting little-known Brit balladeer Greta (played well enough by Keira Knightley, who performs some of the songs).